Mass spectral study of O- and S-aryl dimethylthiocarbamates under electron impact conditions: Newman-Kwart rearrangement in the gas phase

Prabhakar, S. ; Kar, Paramita ; Mirza, S. P. ; Lakshmi, V. V. S. ; Nagaiah, K. ; Vairamani, M. (2001) Mass spectral study of O- and S-aryl dimethylthiocarbamates under electron impact conditions: Newman-Kwart rearrangement in the gas phase Rapid Communications in Mass Spectrometry, 15 (22). pp. 2127-2134. ISSN 0951-4198

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Official URL: http://onlinelibrary.wiley.com/doi/10.1002/rcm.490...

Related URL: http://dx.doi.org/10.1002/rcm.490

Abstract

The electron impact (EI) mass spectra of isomeric S- and O-aryl (2-naphthyl, R-Ph-= aryl, where R = H, NO2, COOCH3, COCH3 and OCH3) dimethylthiocarbamates have been studied in detail. The EI spectra of O-aryl dimethylthiocarbamates include some of the fragment ions that are characteristic of the corresponding S-aryl isomer, which could be explained by a Newman-Kwart rearrangement in the ion source of the mass spectrometer, after ionization. The EI mass spectra of S-aryl dimethylthiocarbamates showed specific fragment ions resulting from cleavage of the molecular ion involving the bond between sulfur and the carbonyl group of the carbamate moiety (α-cleavage). The EI mass spectra of O-aryl dimethylthiocarbamates, however, showed the fragmentation of the molecular ion by α-cleavage involving the bonds on both sides of oxygen atom. Further, the EI mass spectra of O-aryl dimethylthiocarbamates containing an electron-withdrawing substituent (-R) on the aryl group showed a characteristic fragment ion corresponding to [M - R]+.

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